1. Field of the Invention
The present invention relates generally to the production of slide fasteners, and more particularly to an apparatus for forming a row of continuous zigzag coupling elements for slide fasteners from a monofilament of thermoplastic synthetic resin.
2. Description of the Prior Art
Canadian Pat. No. 669,722 and Japanese Patent Laid-Open Publication No. 59-125506 disclose a coupling-element forming apparatus which comprises a heated die wheel having an annular central groove in its peripheral surface and a pair of rows of circumferentially staggered pins disposed one row on each side of the groove. This prior apparatus also comprises a series of working units, i.e. a winding unit for winding a monofilament of thermoplastic synthetic resin around the pins in a zigzag form across the groove, a bending unit for forcing the zigzag monofilament into the groove to form a row of zigzag coupling element blanks having parallel legs interconnected at their lower ends by lower connecting portions, a punching unit for compressing the lower connecting portions against the bottom of the groove to form coupling heads each having a pair of lateral projections, a hammering unit (as occasion demands) for bending upper end portions of the parallel legs laterally outwardly away from each other to form raised connecting portions interconnecting adjacent coupling element blanks, and a discharging unit for removing the thus finalized coupling elements from the die wheel, these working units being arranged around the peripheral surface of the die wheel in this order.
The winding unit of the known apparatus includes a reciprocating guide plate having a guide hole through which the monofilament is guided so as to be shaped into a zigzag form on the peripheral surface of the die wheel. However, since the guide plate and hence the guide hole are reciprocable only in the directions of a generator of the peripheral surface of the die wheel, it is necessary to rotate the die wheel intermittently in timed relation to the reciprocating movements of the guide plate, thus causing only a limited rate of production.